The invention is related to a wire rope holding device that permits relief from wire rope twist while maintaining rope design features under loading conditions.
Wire rope is typically used for transporting and hoisting heavy pieces of machinery or the like. Because hoists utilizing wire rope are complex pieces of machinery, oftentimes containing hundreds of moving parts, proper application, maintenance and handling must be adhered to at all times in order to achieve maximum performance, safety, and service life.
One known condition that must be addressed in hoist mechanisms utilizing wire rope is called xe2x80x9cwire rope twistxe2x80x9d. Wire rope twist is experienced when in loading conditions in combination with reverse bending induces torsion into the wire rope. However, reverse bending around rope drums and sheaves in the hoist mechanism cannot be avoided in hoist mechanisms. For example, referring to FIG. 1, in a standard double reeved design hoist, wire rope 10 is wound around a pulley 12 in a channel 14 formed therein to insure proper engagement with a wire rope sheave (not shown). To operate properly, the wire rope must have fixed end connections in order to maintain its strength under loading conditions. As a result, over time, wire rope twist will weaken the wire rope, thereby leading to a deterioration of operating conditions and safety.
To combat wire rope twist problems, known hoist designs require relief of wire rope twist both prior to installation and periodically during the service life of the wire rope to maintain integrity and to achieve the intended service life. To relieve wire rope twist, the wire rope must be removed from a supply drum or disconnected from the hoist and laid out on a clean surface. This method involves several disadvantages. First, removal of the wire rope results in operation downtime and increased expenses in removing and re-installing the wire rope. Further, when laying the wire rope out to provide the twist relief, great care must be made to insure that debris and dirt are not deposited on the wire rope, leading to degradation of the wire rope in the future. Finally, when the wire rope is re-attached, it must be properly lubricated to insure safe and reliable operation.
Accordingly, to alleviate the above-disadvantages, an improved hoist design that provides for a cost effective means to provide twist relief under a no load condition, but shill provided a fixed end connection under load condition is needed.
A wire rope equalizer system for a conventional hoist mechanism to provide wire rope twist relief is disclosed. In accordance with the invention, the equalizer system includes a base member and a pivoting lever connected thereto. The base member includes downwardly extending corresponding attachment arms that are spaced apart to form a channel therebetween. Extending through the attachment arms is a mounting aperture.
In accordance with one aspect of the invention, the pivoting member includes an upwardly extending attachment lip having a mounting hole therethrough. Attachment lip engages the channel formed by the corresponding attachment arms and the mounting hole aligns with the mounting apertures of the base member. A suitable fastener secures the pivoting lever to the base member such that the pivoting lever may selectively pivot to counteract uneven loads on the hoist mechanism.
In accordance with another aspect of the invention, pivoting lever 40 further includes corresponding mounting extensions positioned on either side of the attachment lip. Each mounting extension has a mounting aperture extending therethrough. Each mounting aperture has a grooved portion that generally corresponds in shape to the rounded end of a ball shank fitting that is secured to the distal end of the wire rope formed in then top surface of each mounting extension. A base of the grooved portion opens into a short throat portion. A bottom section of the throat section has outside edges that are slightly tapered outwardly. Opposite edges of the bottom section are substantially parallel to one another. Throat portion opens into a cone shaped portion that has outside edges that flare outwardly and open towards the bottom surface of the mounting extensions. Opposite edges of the cone shaped portion are substantially parallel to one another.
In operation, each distal end, with ball shank fitted secured thereto, is inserted into the mounting apertures of the pivoting lever with the rounded end of the ball shank engaged with the grooved section of the pivoting lever and the wire rope extending down through the cone shaped portion of the mounting apertures. The ball shank fittings cooperate with the grooved portion to permit selective rotation of the wire rope to counteract wire rope twist when in a no load condition. Further, the outwardly flaring outside edges of the cone shaped section, in cooperation with the generally parallel opposite edges, permit lateral, side-to-side movement to counteract wire rope twist. Moreover, the pivotal connection of the pivoting lever to the base member permits selective vertical movement of the wire ropes to compensate for unequal loading.
An alternative embodiment of the wire rope equalizer system for a single wire rope reeving hoist mechanism is also shown. In a single reeving system, a fixed portion of the hoist mechanism located above wire rope sheaves is provided with a mounting aperture that receives a socket with a distal end of the wire rope. The mounting aperture has a first diameter section that is sized to receive the socket that opens into an intermediate section that opens into a short conical section. The conical section has outside edges that flare outwardly toward the bottom surface of the fixed portion.
In accordance with one aspect of the invention, the socket has a grooved portion that is shaped to correspond to the rounded end of a ball shank fitting secured to the distal end of the wire rope. Grooved portion opens into a short throat portion that generally has a round shape. Throat portion terminates in a short cone shaped section that flares outwardly on all sides.
In operation, the socket is positioned within the first diameter section of the fixed portion of the hoist mechanism with the cone shaped section opening downwardly. The wire rope is threaded through the socket and the mounting aperture of the fixed portion with the ball shank fitting attached positioned in grooved portion of the socket for selective rotational movement. The ball shank fitting cooperates with the grooved portion of the socket and the downwardly opening conical section and cone shaped shaped section to permit movement of the wire rope in any lateral direction to counteract wire rope twist when the hoist mechanism is in a no load condition.